The short version: if you have a recent Cummins 300-340 hp range does your coach hold 6th gear crossing interstate overpasses and mild grades? Or does it downshift at any mild rise?Thanks for your feedback, and if you want to read all the whys and wherefores, the next post I'll drone on. :B

Backstory- we're in the market for a short coach, less than 36 feet. It's our preference (due to the types of parks we enjoy). Likely a Newmar Ventana or Ventana LE or Tiffen RED. We'll pull a large toad. Perhaps new, but we'll also consider going back a few years, but not before DEF engines.I dislike a powertrain that's maxed out on torque and has to shift gears too often. Defeats the whole purpose of a diesel so to speak. And I've operated some trucks like that.The real technical stuff: Most coaches in this range are built with the Allison 2000 series trans, a few have the 3000 Allison. The smaller transmission has limited torque handling capability and is used with the ISB 300 or 340, with peak torque ratings of 600 to 700. The Allison 3000 enables use of the ISB 360 which is 800 lb-ft torque. Which seems like not much difference, right?But here's the thing; the 2000 series requires the use of torque managed engines, which limit the torque when shifting (not a bad thing) and also the torque in certain gears (and this is my concern). The 2000 series trans allows up to 700 lb-ft in gears 3-5. In other conditions it's limited to 575 lb-ft. Limitations on the Allison 3000 are not a concern with the ISB, as the trans can handle 1250 lb-ft and torque management is not required.So... it would appear that the ISB360/Allison 3000 combo can draw on all 800 lb-ft of torque to maintain speed on a grade in any gear, whereas the ISB340/Allison 2500 by comparison can only use 575 lb-ft in 6th gear. That sounds like a recipe for easily dropping out of 6th with the smaller transmission. But does the real world experience match?Thanks for your patience in reading my dissertation, and I appreciate your feedback.

Ductape wrote:The short version: if you have a recent Cummins 300-340 hp range does your coach hold 6th gear crossing interstate overpasses and mild grades? Or does it downshift at any mild rise?Thanks for your feedback, and if you want to read all the whys and wherefores, the next post I'll drone on. :Bneighbour has the 360 ISB in a 2017 tiffin pulls his ford F150 CC 4x4 and says severely lacks power in the hills(loaded pulling truck)I guarantee you it will downshift when in the situations your asking about

I'm running a 2014 Thor Palazzo 33.3. It has a ISB 300 and Allison 2100 MH. I could go to ISB 340 / 700 with the same transmission. I have towed a 2015 Suburban, 2015 GMC Acadia Denali, 2016 Yukon Denali XL, and 2017 Ford Explorer. The I am at my max GCWR when I tow the Yukon and the motor home is empty. The transmission does downshift. I have traveled over the rocky mountains 4 times with this setup (pulling the Acadia) we had no problems. I probably will upgrade to ISB 340.

Thanks for sharing, my pet peeve is not the mountains, as I don't have any objection to gearing down to climb a long grade, that's expected. What I dislike is a gear change just to climb an overpass in flat country, or a moderate rolling hill.A little work with a spreadsheet has given me my answer I believe. Taking as an example recent Newmars:Ventana with the 360/800 will produce 2,486 lb-ft at the axle in 6th gear @ 65 mph. Disregarding accessories and drivetrain losses.Ventana LE with the 340/700 will be only 1,759 lb-ft under the same conditions due to torque limiting in 6th gear.Dropping the LE into 5th gear provides full torque and gets the axle up to 2,476.So in essence 5th on the Allison 2500 equipped coaches will be equivalent of 6th in a coach with the Allison 3000 and the 360/800 engine.That's enough to convince me to seek out a coach with the bigger trans. Not to mention running the weight numbers I'd be over GCWR on the smaller Allison with cargo in the coach plus a 6k toad.

We had a 2014 40ft Red with 340hp. I dont recall it shifting on overpasses but the shifting is pretty seamless from 6-5. We were pulling a crewcab GMC with a couple motorcycles in the truck. I wasnt happy with the power so,went to a Phaeton with ISL.

Wanted: feedback from drivers late model 300-340 Cummins

msturtz
Explorer
Dec 17, 2017
What is being missed here are a few things. When we had a towable we were about 60' long & 8'6" wide with a bumper pull overall length. I drove around downtown Salt Lake City UT & Portland OR including parallel parking. It wasn't fun but I was able to do it without trading paint with anyone. In certain situations other rude drivers were laying on their horn as if that would speed me up. I have also taken our DP off road onto a one lane gravel service road. Again slow speed is key don't be afraid of getting out and looking "GOAL". Many parks won't take longer rigs due to inexperienced drivers rather than actually being unable to accommodate them. Modern rigs have a 55 degree wheel cut. That makes them much easier to turn.
Mile_High
Explorer
Dec 17, 2017
We have the longest Winnie made in 2013 at 43'6" and in the year and half we have had it, I've struggled fitting a few times, even at KOAs. Sometimes its the tight turns that get me, not the length of the driveway. We stayed at a private campground in Truckee, CA and I thought I would never get that thing parked in there.
DSDP_Don
Explorer
Dec 17, 2017
Just to clarify what "tropical36" brought up, there really isn't anything around San Francisco, even for a small rig that is worth staying in. There is a parking lot near the stadium, but it is literally that, a parking lot.

The Petaluma KOA is actually one of the really good spots to see San Francisco either in a Class B or a 45' DP.
tropical36
Explorer
Dec 17, 2017
Ductape wrote:
But that's exactly the point. You ended up in KOA... Thanks but no thanks. :)

I said once and not the norm, with however you one might feel about a particular stay. The thing is, we're not about to go without what we like in a coach, just because it might be a little large for some RV parks and again, far and few in between.
You should see the size of some rigs, inside Glacier NP at their Apgar campground, for instance.
Ductape
Explorer
Dec 17, 2017
But that's exactly the point. You ended up in KOA... Thanks but no thanks. :)
tropical36
Explorer
Dec 17, 2017
A little off topic, but it seems that the only people that claim not being able to find large enough sites in parks are the ones that have never owned a large one of 40ft or more. Occasionally yes, but not the norm.
I do remember once with being on the phone and calling around in the San Francisco area and not having much luck. It was summer and of course most of the CA coast line was pretty active with RV's. Anyway, we went on up to the Petaluma KOA, where you could have brought in a semi without much difficulty. They even had a field for overflow, in case they didn't have a site available upon your arrival. Their van conducted tours of the city, right from the office, so not a problem with being up the road a ways and we used our toad for getting to the ferry, as well. Just saying, that there's always someplace to park, no matter what your size.
msturtz
Explorer
Dec 17, 2017
gutfelt wrote:
msturtz wrote:
I'm running a 2014 Thor Palazzo 33.3. It has a ISB 300 and Allison 2100 MH. I could go to ISB 340 / 700 with the same transmission. I have towed a 2015 Suburban, 2015 GMC Acadia Denali, 2016 Yukon Denali XL, and 2017 Ford Explorer. The I am at my max GCWR when I tow the Yukon and the motor home is empty. The transmission does downshift. I have traveled over the rocky mountains 4 times with this setup (pulling the Acadia) we had no problems. I probably will upgrade to ISB 340.

A suburban weighs more than a 2015 yucon or explorer

I have a Yukon XL it weighs more than a Suburban.
DSDP_Don
Explorer
Dec 17, 2017
"Ductape".....Here are some talking points, or should I say pictures. The first is my 37'Diplomat at the Watchmen Campground inside Zion. You can see there is room for another six feet.

We don't take photos of the coach in the campsite like we use to, so I really don't have that many pictures of the coach itself. In this photo, we're at Yosemite Upper Pines at Thanksgiving. The coach in the background is a 41' Monaco Camelot. My 40' is to the right of the turkey. There are several sites there that will take a 40' coach.

Lastly...I only have the view through the windshield as we enter the Yellowstone west gate.:B We stayed at Fishing Bridge.

The new coaches have a 55+ wheel cut and can really crank around to get into tight spots. Just some confusion for your decision!
Ductape
Explorer
Dec 16, 2017
Thanks, Don. If I could talk both of us into a forty footer I'll skip the Ventana and go directly to the Dutch Star. :B
DSDP_Don
Explorer
Dec 16, 2017
"Ductape"......We owned a 36' 2005 Monaco Diplomat for almost ten years and took it all over the country, including MANY national parks, where we camped inside the park. Those included Yellowstone, Yosemite, Zion, Rocky Mountain etc. We eventually sold that coach and bought a TRUE 40' coach, our Newmar Dutch Star. We've taken that coach to all the same places we took the Diplomat. The Dutch Star is 36" longer than the Diplomat that measured 37'.

In all honesty, sites typically larger than 35' are fewer and far between, but they do exist and we just have to plan ahead at places like Yellowstone.

With all that said, put away your engineering degree and angst, and buy a 40' Ventana with the 400 ISL. All your problems will be solved.

In 4 years of owning the Dutch Star, we haven't regretted adding the 36" in length.